How Does Human Population Affect Climate Change

(Oct 2001) More sizzling summers. Rising body of water levels. Increasingly violent storms and floods. These are merely a few of the many potential impacts of climatic change projected by the Intergovernmental Panel on Climatic change (IPCC), a scientific body created in 1988 past the World Meteorological Association and the Un Environment Plan. The IPCC has discovered changes in regional climates, including temperature increases, and expressed "high confidence" that these changes are affecting many different kinds of ecosystems.¹ The IPCC has besides reported "new and stronger show" that about of the warming of the by l years is owing to human activities, particularly emissions of greenhouse gases into the temper.

What does climatic change mean for the well-existence of human communities effectually the globe? In that location are many answers to this broad question — every community is different, with its own vulnerabilities and capacity for adapting to change. Even then, by looking at projected climate changes in combination with expected changes in the globe's homo population, information technology is possible to proceeds greater insight into this complicated event.

An Array of Impacts

The IPCC has already described a multifariousness of potential climate change impacts on human communities, without taking into account population trends. Some of the about prominent adverse effects could include

• A greater risk of flooding for many communities, due to heavier rainfall from more intense storms as well as rising sea levels every bit polar water ice caps melt
• An increase in deaths due to rut stress
• A reduction in ingather yields in most tropical and sub-tropical regions for about projected increases in temperature
• Decreased water availability for populations in many water-scarce areas
• An increment in the number of people exposed to vector-borne (e.g., malaria) and water-borne (due east.g., cholera) diseases due to changes in temperature and precipitation patterns
• Increased energy demand for space cooling.

Notably, not all of the projected impacts are negative. Some of the beneficial effects that have been projected include

• Increased crop yields in some regions at mid-latitudes for temperature increases of less than a few degrees Celsius
• Potential increases in timber supply from forests that are managed in means that take reward of climate changes
• Increased h2o-availability in some h2o-scarce regions
• Reduced winter mortality in mid- and loftier-latitudes
• Reduced free energy demand for space heating due to college wintertime temperatures.

These changes, if they come to pass, will not occur in a vacuum. Instead, they will occur in tandem with changes in the size, composition, and distribution of the world's human being population. In many cases, these demographic changes could either exacerbate or alleviate the impact of climate modify on man communities. Examining 3 major population trends — urbanization, aging, and growth in less adult countries — suggests that, on balance, demographic change will make humanity more vulnerable to climate change than information technology is today.

Urbanization

Each twelvemonth a higher per centum of the world's population lives in urban areas. The UN projects that 50 percent of humanity will be living in urban areas for the first time e'er by the end of this decade. By 2030, this figure is expected to reach 60 percent. This trend is due both to rural-to-urban migration likewise every bit natural increment (the number of births minus deaths) in urban areas. Urbanization tin be seen both in the proliferation of towns and cities, which is the primary design in China, also as the expansion of existing urban areas. In 1975, only five cities had more than 10 million inhabitants; by 2015, there will exist 24.

Despite a wide range of regional variation, the trend of urbanization is apparent in every major world region (see Effigy ane).

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Effigy ane
Regional Trends in Urbanization

Note: The definition of "urban" varies by country, so the projections here are suggestive of regional differences in urbanization rates rather than a definitive documentation of them.
Source: UN, World Urbanization Prospects: The 1999 Revision, 2000.

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The trend toward urbanization could influence the impact of climate modify in several ways. For instance, congestion and heat-absorbing cobblestone brand cities mostly hotter than the surrounding countryside. As more than people inhabit urban areas, the number of people vulnerable to heat stress is thus likely to rise: a problem that will be compounded by rising temperatures due to climatic change. College temperatures are particularly hard for cities that have less feel with intense summertime heat. The oestrus moving ridge that hit Chicago in July 1995, for case, contributed to the deaths of more than 500 people.

Of course, in some cases the flow of people from rural to urban areas may really increase access to air conditioning, as has happened in cities like Hong Kong and Taipei. Such improvements are critically dependent on increasing abundance and development, even so. Sprawling shantytowns, like those that surround Sao Paulo and Jakarta, offering little refuge from ascension temperatures.

Since urban areas feature high concentrations of people, they are also more than deadly during natural disasters. If climatic change leads to more frequent and intense storms and floods, high-density population centers volition be amongst the near exposed. In November 1998, Hurricane Mitch devastated Tegucigalpa, Republic of honduras, and a number of other Central American cities, killing several hundred and perchance thousands of people. One written report estimated that the mudslides unleashed by the tempest had destroyed more than 48,000 homes in Tegucigalpa, 20 per centum of the urban center's total. Such urban catastrophes could become more mutual.

Cities in less developed countries are particularly vulnerable to natural disasters. As noted past Martin Brockerhoff in PRB'due south Population Message, "An Urbanizing World," many cities in the less developed world were established in coastal areas most suitable for trading — Mumbai (Bombay) and Shanghai are prime number examples. Since rising body of water levels, flooding, and storms unduly affect coasts, they represent an even greater threat to the urban residents of these cities. In improver, less developed countries oft have less stringent building standards, making their cities especially dangerous places to be when natural disasters strike. Many of the homes that were destroyed by Hurricane Mitch, for example, were hovels built on the outskirts of Tegucigalpa.

Aging

Another primal population tendency in the 21st century will be crumbling. Due to the mail service-World State of war Two baby boom in Europe, the Us, and Japan, likewise as falling fertility rates in less developed countries afterwards 1970, many countries will have to contend with populations that comprise rising proportions of older citizens. This trend is most pronounced in Japan, but it is also notable in a number of other countries, including both People's republic of china and India (come across Figure 2).

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Figure ii

Population Aging Worldwide

Source: UN, World Urbanization Prospects: The 2000 Revision, forthcoming, 2001 (medium scenario).

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The implications of population aging for the touch on of climatic change are not entirely clear, but there are at least two issues that should be considered. Commencement, older people are physically more vulnerable to farthermost heat, and then population aging could exacerbate increases in oestrus-stress mortality brought on by climate alter. Higher temperatures also exacerbate outdoor air pollution such every bit ozone, which also disproportionately affects older people. On the other hand, older individuals are as well more than vulnerable to cold weather condition, and then a warming tendency in colder latitudes could subtract wintertime mortality rates, particularly in countries such as Russia.

A second result to consider is the pressure level posed past an aging population on public finances. Population crumbling implies a relative decrease in the number of working-age individuals and a relative increase in the number of retirees, a situation that could pb to falling taxation revenues and increasing need for public services. In Japan, the pronounced aging underway has influenced the government'southward credit rating as analysts worry about how the country will care for its increasing number of elderly citizens. Even in countries with no social security system, population aging would be likely to erode the government's fiscal position as taxation acquirement declines. The fiscal constraints imposed by aging populations will arrive more hard for governments to finance measures to mitigate the impacts of climate change.

Population Growth in Less Developed Countries

The world's population currently increases by 83 meg people each year, but merely 1 meg of them live in more developed countries. The population of the less developed world is thus growing much more rapidly than that of more adult regions. Today, citizens of less adult countries outnumber those of more than developed countries 4.9 billion to 1.two billion. In 2050, those figures will exist seven.viii billion and 1.2 billion, respectively, according to PRB'southward 2001 Globe Population Data Canvass. Of the most iii billion people the world will add in the next l years, South Asia and Africa will each business relationship for roughly one billion.

The concentration of population growth in less developed regions means that an increasing number of people live in countries with the least ability to adjust to climate change. The range of measures that could be needed to mitigate the impacts of climate change run the gamut: air conditioner purchases, changes in agricultural practices, structure of houses on stilts, relocation programs, development of storm and flood early alert systems, and replenishment of eroded beaches, to name just a few. Besides lacking the financial resource to undertake many of these measures, many less developed countries also lack the scientific expertise, effective public institutions, infrastructure, and technology needed to brand adaptation measures work. Consequently, the brunt of the deleterious impacts of climate modify volition be borne by countries with an increasing proportion of the world's population.

Bangladesh provides a dramatic case of this problem. With 134 million people, information technology is already 1 of the world'due south more populous countries, and its population is projected to surge to 209 one thousand thousand by 2050. The Ganges-Brahmaputra river delta in detail is one of the near densely populated areas in the globe. Still this delta, which occupies much of southern Bangladesh, is likewise tremendously vulnerable to climate change. The impact of rising sea levels could be disastrous, causing all-encompassing flooding and erosion as well every bit salinization of agricultural land and freshwater supplies. Co-ordinate to the United nations Environs Plan, a 150-centimeter rise in sea levels could readapt more 30 one thousand thousand people. Bangladesh can scarcely afford to tackle these problems on its own: With a gross national income of only $47 billion in 1999, People's republic of bangladesh's economic system is the same size as that of Peru, even though it has five times as many people.

To be sure, while the residents of industrialized countries may non be as hard hitting as those of less developed countries, climate modify would not exit the more developed earth unscathed. In the United States, for example, parts of southern Florida and Louisiana would exist submerged by a 1-meter ascension in sea level. And there could be unwelcome indirect effects also. If less adult countries are disproportionately hurt by climate change, the political backlash against industrialized countries that are leading carbon-emitters (especially the United States) could be considerable. Less developed countries are already making a diversity of demands for bounty, a movement probable to gather strength as climatic change continues and its effects are felt more strongly.

On remainder, the three population trends examined higher up — urbanization, aging, and growth in less adult countries — seem likely to increase humanity's vulnerability to climate change over the side by side several decades. While sure aspects of climate change could prove benign to some communities, the most obvious argent lining — warmer winters at colder latitudes — will not assist most people in the less developed world. Given this prospect, the tasks of preventing future climate change and identifying inexpensive ways of adapting to information technology appear all the more pressing.

The Science of Climate Change

Most of the dominicus'south radiation passes through Earth's atmosphere to warm the planet. Earth's surface in plow reflects this energy back toward space in the form of infrared (heat) radiations. Certain gases in the temper, such as carbon dioxide and water vapor, absorb and re-emit this free energy, which slows the process of releasing the solar free energy back into infinite. This natural trapping of estrus keeps the planet surface warmer than information technology would otherwise be, making it more hospitable to life.

Over the past two centuries, all kinds of human being activities — from powering steam engines or driving a car to air conditioning a business firm or surfing the World wide web — have added to this "greenhouse" effect. The Industrial Revolution, particularly the widespread use of fossil fuels such as oil and coal, has led to the release of enormous amounts of heat-absorbing gases into the atmosphere. The iv greenhouse gases whose atmospheric concentrations are nigh influenced by human activities are

• Carbon dioxide or CO2 (produced by burning solid waste, woods and wood products, and fossil fuels such as oil, natural gas, and coal)
• Methane or CH4 (emitted by livestock or by the decomposition of organic wastes in municipal solid waste landfills)
• Nitrous oxide or N2O (generated by the combustion of fossil fuels and solid waste)
• Chlorofluorocarbons (also called CFCs, manufactured by manufacture for use in coolants and insulation).

Global emissions of carbon dioxide from human activities have increased more than k-fold, from 660 million to 931 billion metric tons between 1795 and 1995, according to the U.S. Department of Energy's Carbon Dioxide Data Analysis Eye (CDIAC). As a result, atmospheric concentrations of carbon dioxide take risen substantially over the past two centuries.

The implications of rising levels of greenhouse gases in the atmosphere have received a bully deal of scientific attending over the past decade. In 1995, the IPCC concluded in its Second Assessment Report that "the balance of show propose[ed] a discernible human being influence on the global climate" — a conclusion that helped atomic number 82 to the setting of greenhouse gas emissions targets in the Kyoto Protocol.

The IPCC'south Third Cess Report, completed in October 2000, cited "stronger testify" than ever earlier linking human activeness to climate change. It also argued that man-made greenhouse gases have probably already "contributed substantially to the observed warming over the last 50 years." The IPCC as well revised its forecast of the amount of global warming that is probable: If greenhouse gas emissions are not curtailed, Earth'due south average surface temperatures tin can be expected to increase by 1.iv to v.8 degrees Celsius (2.5 to x.4 degrees Fahrenheit) by 2100, substantially more than the panel estimated in its 1995 study.

In response to a asking from the Bush administration, an expert panel at the U.S. National Inquiry Council (NRC) conducted an evaluation of the state of climate modify science in early on 2001, leading to the publication of Climate Modify Science: An Analysis of Some Key Questions. This report agreed with the IPCC's assertion that greenhouse gases were accumulating in the atmosphere as a upshot of human activities, leading to rise surface air temperatures and subsurface bounding main temperatures. The report also stated that the climate changes observed over the past several decades were "likely mostly due to man activities," though a "significant part" of these changes might as well reflect natural variability. Regarding hereafter climatic change, the NRC panel noted that "homo-induced warming and associated sea level rises are expected to continue through the 21st century," although electric current projections "should be regarded as tentative and discipline to future adjustments."

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Bingham Kennedy, Jr. is a former acquaintance editor at the Population Reference Bureau.

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Reference

1. Intergovernmental Panel on Climate change, Climate change 2001: Impacts, Accommodation, and Vulnerability, a Report of Working Group Two of the Intergovernmental Panel on Climate Change (Geneva: IPCC, Feb 2001), accessed online at world wide web.ipcc.ch, on August 15, 2001.

For More Data

For the Assessment Reports cited in this article, visit the Intergovernmental Panel on Climatic change at www.ipcc.ch

The U.South. Department of Energy's Carbon Dioxide Data Analysis Eye (CDIAC) website can be constitute at cdiac.esd.ornl.gov

Source: https://www.prb.org/resources/climate-change-impacts-emerging-population-trends-disaster/

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